Heat-recoverable composition coupling device

ABSTRACT

Described herein are heat recoverable composite couplings comprising an outer, tubular heat-shrinkable sleeve and a hollow insert member adapted to receive plural substrates. The insert member has a tapered surface to allow it to accommodate substrates of different sizes. Recovery of the outer member forces the insert member into secure contact with the substrate forming a union between the substrates.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 552,711 filed on Nov. 17, 1983, now abandoned, a division of application Ser. No. 29,212 filed on Apr. 12, 1979, now U.S. Pat. No. 4,455,041, which is a continuation of application Ser. No. 608,206 filed on Aug. 22, 1975, and now abandoned.

FIELD OF THE INVENTION

This invention relates to heat recoverable composite coupling devices.

BACKGROUND OF THE INVENTION

The composite coupling devices described and claimed in my aforementioned applications, comprise a "driver", or heat-recoverable member, made from a memory metal and a second, sleeve member, usually an insert member, which is so constructed, and/or fabricated from such a material, that it enhances the coupling of the composite device to a substrate or substrates. Typically, the "driver" member and the "insert" member are both generally tubular and the insert member is provided with teeth and/or is made from a gall-prone material and/or is provided with portions, such as slots or grooves, of relative weakness, and/or is made from a material with desirable properties, e.g. electrical properties, having regard to the particular application/of the composite coupling device.

As is explained in the above applications, "memory metals" are alloys which exhibit changes in strength and configurational characteristics on passing through a transition temperature, in most cases the transition temperature between the martensitic and austenitic states, and can be used to make heat-recoverable articles by deforming an article made from them whilst the metal is in its martensitic, low temperature, state. The article will retain its deformed configuration until it is warmed above the transition temperature to the austenitic state when it will recover towards its original configuration. The deformation used to place the material in the heat-unstable configuration is commonly referred to as thermally recoverable plastic deformation and can also, in certain cases, be imparted by introducing strains into the article above the transition temperature, whereupon the article assumes the deformed configuration on cooling through the transition temperature. It should be understood that the transition temperature may be a temperature range and that, as hysteresis usually occurs, the precise temperature at which transition occurs may depend on whether the temperature is rising or falling. Furthermore, the transition temperature is a function of other parameters, including the stress applied to the material, the temperature rising with increasing stress.

Amongst such memory metals there may especially be mentioned various alloys of titanium and nickel which are described, for example, in U.S. Pat. Nos. 3,174,851, 3,351,463, 3,753,700, 3,759,552, British Pat. Nos. 1,327,441 and 1,327,442 and NASA Publication SP 5110, "55-Nitinol-The Alloy with a Memory, etc." (U.S. Government Printing Office, Washington, D.C. 1972), the disclosures of which are incorporated herein by reference. The property of heat recoverability has not, however, been solely confined to such titanium-nickel alloys. Thus, for example, various copper-based alloys have been demonstrated to exhibit this property in, e.g. N. Nakanishi et al, Scripta Metallurgica 5, 433-440 (Pergamon Press 1971) and such materials may be doped to lower their transition temperatures to cryogenic regimes by known techniques. Similarly, type 304 stainless steels have been shown to enjoy such characteristics, E. Enami et al, id at pp. 663-68. These disclosures are similarly incorporated herein by reference.

In general, the alloys are chosen to have transition temperatures between the boiling point of liquid nitrogen, -196° C., and room temperature as the lowest temperature likely to be encountered in operation, i.e. between -196° C. and -75° C. in many aerospace applications. This enables the articles made from the alloys to be deformed to the configuration from which recovery is desired, and stored, in liquid nitrogen and yet insures that after heat recovery there is no danger of loss of mechanical strength during use by reason of the article encountering a temperature at which it reverts to the martensitic state.

However, storage of the deformed article in liquid nitrogen is inconvenient. Recently processes have been developed by which metallic compositions, particularly certain copper-based alloys, can have the transition temperature at which they revert to the austenitic state transiently elevated from the normal temperature at which this occurs to a higher temperature, typically above room temperature. Subsequently recovery requires that the article be heated. Such alloys are referred to as being "preconditioned". Procedures by which they are preconditioned are described in U.S. applications by G. B. Brook et al filed 19th February 1975 entitled "Heat Treating Method", Ser. No. 550,847; And now abandoned "Mechanical Preconditioning Method", Ser. No. 550, 555 now U.S. Pat. No. 4,036,669 issued July 19, 1977; and "Austenitic Aging of Metallic Compositions", Ser. No. 550,556 now U.S. Pat. No. 4,067,752 issued Jan. 10, 1978; the disclosures of which are incorporated by reference.

As indicated above, by application of a preconditioning process to an alloy its transition temperature can be elevated. However, once recovery has been brought about by heating the article through its new transition temperature, the alloy's response to temperature change reverts to that it possessed prior to preconditioning. Accordingly, it remains austenitic until cooled to the temperature at which transition to martensite normally occurs, typically chosen to be at 0° C. or below depending upon the temperature environment likely to be encountered.

A typical application for the composite couplings described in the aforementioned Martin applications is to join tubular or cylindrical substrates. Properly dimensioned, these couplings can be employed to join substrate that vary greatly in size. For example, they might find application in joining tubing sections that could be used for hydraulic systems in aircraft. They can also be used to join sections of pipe of very large dimension.

In many situations the tolerance criteria for the cylindrical substrate to be joined are such that there can be significant variation in size between sections, for example on the order of 5% or even more, and the substrate may be significantly out of round. Also, it is frequently desired to connect substrates that vary somewhat in size. Accordingly, there is a need for composite couplings capable of accommodating such irregularities or variations in the substrate. The principal object of this invention is to provide such devices.

SUMMARY OF THE INVENTION

The present invention provides composite couplings capable of meeting this need. These couplings comprise a heat shrinkable driver of a memory metal such as described in the Background of the Invention, in combination with a generally cylindrical insert member that has a tapered surface, which may be either the interior or exterior surface, in order that it can cooperate with the substrate itself, yet another insert having an inverse taper, or the driver in order to accommodate differences in size between sections of cylindrical substrate or compensate for their being out of round. To improve the retention of the substrate within the coupling, an insert may be provided with serrations or teeth or be made from a gall-prone member so that the occurrence of galling between it and the substrate strengthen the joint. In presently preferred embodiments of the invention, the insert itself comprises at least two concentrically disposed members. The outer member of the concentric pair is tapered on its inner surface and the inner member tapered on its outer surface with slopes that allow the surfaces to contact each other as one is moved relative to the other along their common longitudinal axis. By reason of this movement, the coaction of the tapered surfaces of the insert members can cause the inner member to be deformed in order to conform and more securely engage the insert to the substrate prior to recovery of the driver. In this way, less of the force exerted by the driver is expended initially deforming the insert to conform to the substrate and a more uniform force is exerted upon recovery of the driver.

In particularly preferred embodiments, a portion of the insert is threaded and provided with tightening nuts to facilitate the initial deformation of the insert prior to recovery of the driver.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments according to the present invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which briefly described:

FIGS. 1a and 1b illustrate a composite coupling for joining cylindrical substrates that differ in diameter;

FIG. 2 illustrates another form of composite coupling for joining cylindrical substrate;

FIG. 3 illustrates a composite coupling for fluid tight connections;

FIG. 4 illustrates yet another composite device for coupling cylindrical substrates;

FIG. 5 illustrates a further form of coupling devices; and

FIG. 6 illustrates another form of coupling device.

Referring to the drawings:

FIGS. 1a and 1b illustrate the use of a composite device according to the present invention for joining tubular substrates. As shown in FIG. 1a, tapered insert 1 to heat recoverable driver 2 has a constant out-side diameter but is tapered internally from a maximum internal diameter at its ends to a minimum internal diameter near its center. As a result of this internal taper, each end of insert 1 is capable of receiving tubular substrates 3 and 4 which may be of the same or different diameter. Also by reason of its taper, insert 2 is capable of accommodating a wider range of substrate diameters than would an insert of constant internal diameter.

As shown in FIG. 1b, insert member 1 may be provided with serrations or teeth to enable it to better grip the substrate when recovery has occurred. Insert member 2 may also be made of a gall-prone metal relative to the substrate.

For optimal attainment of the advantage conferred by the use of gall-prone inserts, the surface roughness of the insert is desirably made like that of one or more of the surfaces it adjoins in the particular application. For example, for the hydraulic conduitry for which the composite couplings are preferably employed, the generally uniform surface of the insert preferably exhibits profilometer roughness not greater than about 125 micro-inches, most preferably not greater than about 63 micro-inches.

Another device according the present invention after its recovery is shown in FIG. 2 in which the insert comprises two members 5 and 6. The outer member 5 is tapered internally from a maximum internal diameter at one end to a minimum internal diameter at the other. As shown, member 5 is provided with longitudinal slots 7 at the end of maximum internal diameter to facititate its deformation upon recovery. Inner member 6 is provided with an outer taper complementary to that of member 5 in that it tapers from a maximum outside diameter at one end to a minimum at the other. Member 6 is provided with terminal longitudinal slots 8 at either end to facilitate its deformation. As shown in FIG. 2, inner member 6 is provided with teeth to inhibit the withdrawal of tubular members 9 and 10 after recovery by forming circumferential dents 11 and 12.

Prior to recovery of driver 13, members 5 and 6 are wedged closely together, member 5 acting upon member 6 to compensate for variations in the substrate's outside diameter or substrate ovalness.

Another device according to the present invention that will accommodate cylindrical substrates having a large variation in outside diameter is shown in FIG. 3. As shown, the insert is comprised of three tapered parts, 14, 15 and 16. Outer member 14 is provided with threaded end portions 17 and 18 and tapers internally between the threaded portions to a minimum inside diameter at its center. As shown, member 14 is provided with longitudinal slots between its threaded sections to facilitate is deformation by the driver upon its recovery. Inner members 15 and 16 are tapered on their outside from a maximum outside diameter at one end to a minimum at the other and preferably are provided with terminal longitudinal slots as shown. As shown in FIG. 3, the inner members can be provided with teeth to engage the substrate, tubular sections 19 and 20.

Prior to recovery, the tubular substrates, which can have the same or different outside diameter are introduced into the aperture formed by members 15 and 16. Tightening nuts 21 and 22 provide means by which members 15 and 16 can be advanced into member 14 to initially engage substrate sections. It will be apparent that the furthest advance of members 15 and 16 is dictated by the diameter of the substrate sections. If the substrate is to carry fluid, O-ring type gaskets 23 and 24 can be provided for sealing purposes. To protect member 14 from a corrosive fluid, a toothed ring 25 can be inserted between members 15 and 16 to make the joint fluid tight. Of course ring 25 must be of a material resistant to the fluid. Between the tightening nuts and members 15 and 16 can be disposed washers 26 and 27. When ring 25 is employed, gaskets 23 and 24 may be omitted.

In FIG. 4, there is shown a variant of the device of FIG. 3. As shown in FIG. 4, the insert again comprises 3 parts. However, the inner member 28 of the insert has threaded ends 29 and 30 to receive tightening nuts 31 and 32 which are employed to advance tapered outer members 33 and 34. By their advancement, insert members 33 and 33a force member 28 into close contact with substrate sections 34 and 35 prior to recovery of driver member 36. Preferably, the insert members are slotted to facilitate deformation.

In the devices of both FIGS. 3 and 4, the provision for oppositely tapered members provide means by which the inner member can be deformed prior to recovery of the driver to conform to the substrate. Thus when recovery is caused to occur, a larger portion of the recovery force can be asserted to further engage the insert and substrate rather than being partially dissipated by having to first deform the insert.

Another device according to the present invention is depicted in FIG. 5. In that device, the inner member 37 of the insert is tapered from a maximum outer diameter at its ends to a minimum diameter at its center. As shown, it is provided with teeth and has longitudinal slots. Outer members 38 and 39 are internally tapered to cooperate with member 37. Outer members 38 and 39 are threaded at their ends to receive tightening nuts 40 and 41. The action of these nuts is to withdraw elements 38 and 39 which has the effect of deforming inner member 37 to cause it to engage substrates 42 and 43. When this has been accomplished, recoverable driver 44 is warmed above its transition temperature to provide the final pressure required by the coupling.

FIG. 6 illustrates another variant of the present invention in which the insert comprises a single member 45, preferably slotted, which is generally cylindrical and externally tapered from a minimum outside diameter at its ends to a maximum at its center. The insert is threaded from its ends to receive nuts 46, and 47 which also functions as heat recoverable drivers, i.e. they are capable of recovering to a smaller dimension. Center section 48 of insert 46 is provided with lugs to allow it to be held without rotation when the nuts are installed. Preferably insert 46 is provided with internal teeth as shown.

The nuts are rendered heat recoverable by mandrel expansion while the nut is at a temperature at which it exists in the martensitic state. The threads can be protected during expansion by providing the nut with a threaded liner of the same alloy that can be screwed into the out of the nut. The nut is preferably preconditioned after expansion to elevate the temperature at which it reverts to martensitic to insure that the transition does not prematurely occur during the installation of the coupling.

Once the substrates 49 and 50 have been inserted in the aperture defined by insert 45, the nuts are tightened to initially deform the insert and adapt its conformation to the irregularities of the substrates. The nuts are then heated to occassion their recovery and thereby tightly engage the insert and substrates.

The couplings previously described are but illustrative of the many forms the present invention may take. It will be apparent that the composite couplings of this invention are suited to many applications where the joining of cylindrical substrates is desired. For example, they might be employed to join solid or tubular structural members or cable. However, it is presently felt that the preferred application for these couplings is in the union of hollow member adapted to convey fluids, for example fluids in hydraulic systems or pipelines. 

I claim:
 1. A composite device for securely engaging at least one substrate which comprises:(a) at least one tubular, heat-recoverable, metallic compression sleeve; and (b) at least one tubular, metallic insert snugly and concentrically disposed within, adjacent to, and in contact with the compression sleeve so that when the compression sleeve is heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrate, the insert having an inner surface and an outer surface, the inner surface of said insert being tapered and the diameter of the outer surface being substantially constant, wherein said insert is structurally weakened to facilitate its deformation by said sleeve.
 2. A composite device for securely joining substrates which comprises:(a) at least one tubular heat recoverable metallic compression sleeve; (b) a hollow, tubular metallic insert snugly and concentrically disposed within, adjacent to and in contact with the compression sleeve so that when the compression sleeve is heat-recovered by being heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrates, wherein said insert has a inner surface, an outer surface, and a substantially constant inner diameter, and the outer surface of the insert tapers from a minimum diameter near its ends to a maximum diameter inboard said ends; and (c) a pair of hollow members sized for concentric disposition between said sleeve and said insert on either side of the maximum diameter of said insert, each member having an outer end and an inner end and a substantially constant outer diameter and an inner surface that tapers from a minimum diameter at the outer end of the member to a maximum diameter at the inner end of the member.
 3. A composite device according to claim 2 wherein the inner surface of said insert has a plurality of teeth thereon.
 4. A composite device according to claim 2 wherein said insert is made from a gall-prone metal.
 5. A composite device according to claim 2 wherein said insert is provided with urging means to urge said hollow members into close contact with said insert thereby causing the insert to more closely conform to the surface of said substrates prior to the recovery of said compression sleeve.
 6. A composite device according to claim 5 wherein said urging means comprise threaded ends on said insert and a pair of threaded nuts adapted to be advanced on said threaded ends and thereby advance said hollow members towards each other.
 7. A composite device for securely engaging at least one substrate which comprises:(a) at least one tubular heat-recoverable metallic compression sleeve; (b) a hollow tubular metallic insert concentrically disposed within said sleeve, wherein said insert has an inner surface and an outer surface and a substantially constant inner diameter, the outer surface of the insert tapering from a maximum diameter near one of its ends to a minimum diameter near its other end; and (c) a hollow member adapted for concentric disposition between and proximate to said compression sleeve and said insert, said hollow member having a substantially constant outer diameter and an inner surface that tapers from a minimum diameter near one of its ends to a maximum diameter near its other end, said insert and said hollow member being disposed so that said hollow member can wedge said insert into closer contact with said substrate; so that when said sleeve is heat-recovered by being heated above its transition temperature, the hollow member is urged into contact with the insert and the insert is thereby altered in at least one of its dimensions and is driven inwardly for securely engaging and forming a gas-tight seal with the substrate.
 8. A composite coupling according to claim 7 wherein said hollow member and said insert are made from a gall-prone metal.
 9. A composite coupling according to claim 7 wherein the inner surface of said insert has a plurality of teeth thereon.
 10. A composite device for joining substrates which comprises:(a) at least one tubular heat recoverable metallic compression sleeve; (b) a hollow tubular metallic insert snugly and concentrically disposed within, adjacent to, and in contact with the compression sleeve so that when said sleeve is heat-recovered by being heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrates, wherein said insert has an inner surface and an outer surface and a substantially constant inner diameter, the outer surface of the insert tapering from a minimum diameter near the ends of the insert to a maximum diameter inboard said ends of the insert, said outer surface being threaded; and (c) said compression sleeve comprising a pair of members threaded on their inner surface and adapted to be advanced upon the threaded, tapered surface of the insert to deform it into closer contact with the substrates prior to the recovery of said compression sleeve.
 11. A composite device according to claim 10 wherein the inner surface of said insert has a plurality of teeth thereon.
 12. A composite device for joining substrates which comprises:(a) a tubular heat recoverable metallic compression sleeve; (b) a hollow tubular metallic insert sized for concentric disposition within said sleeve adapted to contact and form a secure gas-tight connection between said cylindrical substrates when said sleeve is heated above its transition temperature, said sleeve effecting joinder of the substrates by deforming the insert when so heated, the insert having an inner surface and an outer surface, wherein said insert has a substantially constant inner diameter and the outer surface of the insert tapers from a maximum diameter near its ends to a minimum inboard said ends; and (c) a pair of hollow members for insertion from opposite ends of said device and sized for concentric disposition between said sleeve and said insert, each hollow member having an outer end, an inner end, a substantially constant outer diameter, and an inner surface that tapers from a maximum diameter at its outer end to a minimum diameter at its inner end.
 13. A composite device according to claim 12 wherein the inner surface of the insert has a plurality of teeth thereon.
 14. A composite device according to claim 12 wherein said insert and said hollow members are made from a gall-prone metal.
 15. A composite coupling according to claim 12 wherein said hollow members are provided with urging means to urge them into close contact with said insert and thereby urge said insert into close contact with said substrates prior to recovery of said sleeve.
 16. A composite coupling according to claim 15 wherein said urging means comprise (1) threaded ends on each of said hollow members extending beyond the ends of said insert and said sleeve, and (11) a pair of threaded nuts adapted to be advanced on said threaded ends and partially withdraw said hollow members from said coupling device, said withdrawing causing said hollow members to deform said insert into engagement with said substrate.
 17. A composite device for coupling to a substrate which comprises:(a) a tubular heat recoverable metallic compression sleeve having a substantially constant inner diameter; and (b) a hollow tubular metallic insert sized for concentric disposition within the compression sleeve so that when the compression sleeve is heat recovered by being heated above its transition temperature the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging the substrate, the insert having a substantially constant inner diameter and an outer surface that is tapered.
 18. The device of claim 17 further comprising at least one hollow member sized for concentric disposition between the sleeve and the insert, the hollow member having a tapered inner surface complementary to the taper of the outer surface of the insert so that the hollow member can wedge the insert into closer contact with the substrate.
 19. The device of claim 18 in which the outer surface of the insert is threaded, the device including a tightening nut, the inner surface of the tightening nut being correspondingly threaded so that the tightening nut can be advanced upon the threaded surface of the insert thereby advancing the hollow member for deforming the insert into close contact with the substrate prior to recovery of the compression sleeve.
 20. The device of claim 17 wherein the outer surface of the insert tapers from a maximum outer diameter near one of its ends to a smaller outer diameter inboard said end.
 21. A composite device for securely engaging at least one substrate which comprises:(a) at least one tubular, heat-recoverable metallic compression sleeve; and (b) at least one tubular, metallic insert snugly and concentrically disposed within, adjacent to and in contact with the compression sleeve so that, when the compression sleeve is heat-recovered by being heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrate, the insert having an interior surface and an exterior surface, with the exterior surface being tapered.
 22. A composite device for securely engaging at least one substrate which comprises:(a) at least one tubular, heat-recoverable metallic compression sleeve; and (b) at least one tubular, metallic insert snugly and concentrically disposed within, adjacent to and in contact with the compression sleeve so that, when the compression sleeve is heat-recovered by being heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrate, the insert having an interior surface and an exterior surface, at least one of the surfaces of the insert being tapered, and the insert being structurally weakened to facilitate its deformation by the sleeve.
 23. A composite device for securely engaging at least one substrate which comprises:(a) at least one tubular, heat-recoverable metallic compression sleeve; and (b) at least one tubular, metallic insert snugly and concentrically disposed within, adjacent to and in contact with the compression sleeve so that, when the compression sleeve is heat-recovered by being heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrate, the insert having an interior surface and an exterior surface, at least one of the surfaces of the insert being tapered, the insert being provided with at least one continuous radial tooth circumferentially formed about the longitudinal axis of the insert on the interior surface of the insert so that, upon heat recovery of the compression sleeve, the insert and the interior surface tooth directly contact and form a gas-tight seal with the substrate, and the insert also being provided with at least one tooth circumferentially formed about the longitudinal axis of the insert on the exterior surface of the insert.
 24. A composite device for securely engaging at least one substrate which comprises:(a) at least one tubular, heat-recoverable metallic compression sleeve; and (b) at least one tubular, metallic insert snugly and concentrically disposed within, adjacent to and in contact with the compression sleeve so that, when the compression sleeve is heat-recovered by being heated above its transition temperature, the insert is altered in at least one of its dimensions and is driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with the substrate, the insert having an interior surface and an exterior surface, at least one of the surfaces of the insert being tapered, the insert being provided with at least one continuous radial tooth circumferentially formed about the longitudinal axis of the insert on the exterior surface of the insert.
 25. A composite device for securely joining a pair of substrates which comprises:(a) a tubular heat-recoverable, metallic compression sleeve; and (b) a plurality of tubular metallic inserts snugly and concentrically disposed with adjacent to and in contact with the compression sleeve so that when the compression sleeve is heat-recovered by being heated above its transition temperature, each insert is altered in at least one of its dimensions and is driven inwardly by the sleeve for securely engaging and forming a gas-tight seal within the substrates, the inserts having an exterior surface and an interior surface, at least one of the surfaces of each insert being tapered.
 26. A method for forming a connection to at least one substrate comprising the steps of:(a) placing on the exterior of the substrate a composite device comprising (i) a tubular heat-recoverable metallic compression sleeve; and (ii) a tubular metallic insert snugly and concentrically disposed within, adjacent to and in contact with the compression sleeve, the insert having an interior surface and an exterior surface, the exterior surface of the insert being tapered; and (b) heat-recovering the compression sleeve by heating the compression sleeve to above its transition temperature for altering the insert in at least one of its dimensions and driving the insert inwardly for securely engaging a forming a gas-tight seal with the substrate.
 27. The method of claim 26 wherein the insert is driven into direct engagement with the substrate.
 28. The method of claim 26 wherein there is a member disposed between the insert and the substrate so that the altering of compression sleeve in step (b) causes the member to securely engage and form a gas-tight seal with the substrate.
 29. A method for connecting a pair of substrates comprising the steps of:(a) placing on the exterior of the substrates a composite device comprising (i) a tubular, heat-recoverable metallic compression sleeve, and (ii) a tubular metallic insert snugly and concentrically disposed within, adjacent to, and in contact with the compression sleeve, and insert having an interior surface and an exterior surface, the exterior surface of the inset being tapered; and (b) heat-recovering the compression sleeve by heating the compression sleeve to above its transition temperature for altering the insert in at least one of its dimensions and driving the insert inwardly for securely engaging and forming a gas-tight seal with both substrates.
 30. The method of claim 29 wherein the insert is driven in direct engagement with the substrates.
 31. The method of claim 29 wherein there is a member disposed between the insert and the substrate so that the altering of the compression sleeve in step (b) causes the member to securely engage and form a gas tight seal with both substrates.
 32. An assembly comprising:(a) a pair of substrates; (b) a tubular, metallic compression sleeve that has been heat-recovered by being heated above its transition temperature; and (c) a tubular, metallic insert, the insert being snugly and concentrically disposed within, adjacent to, and in contact with the interior surface of the compression sleeve and in contact with the exterior surface of both substrates, the insert having an interior surface and an exterior surface, the exterior surface of the insert being tapered; wherein, when the compression sleeve was heat-recovered by heating above its transition temperature, the insert was altered in at least one of its dimensions and was driven inwardly by the heat-recovered sleeve for securely engaging and forming a gas-tight seal with both substrates.
 33. The assembly of claim 32 wherein the insert is in contact with both substrates. 